I never saw this thread back when you made it, sorry about that. If it were me and I was going out there in March, there's one river I'd make sure to fish...the Umpqua. It flows through Roseburg. It's a big river, you'll want to fish it with a guide, and it has tons of steelhead and big ones.
I have friends who fish the Umpqua every March, and they finally convinced me to give it a try. I took my father in law, who had never been steelhead fishing. I hooked the first fish, and handed him the rod since he'd never caught a steelie. Imagine my regret when I saw this HUGE steelhead come up and roll. It never jumped, but when we finally had it in the net, the guide was going on and on about how few he ever gets that are this big. It was right at 40" long, and full of roe. I told the guide to release the fish as soon as I took a photo, and I thought my father in law was going to cry when he saw that big hen go back into the water. The guide then asked me if I realized how big that fish was and I replied "Yeah, close to 20 pounds." The guide said it was more like 21 or maybe even 22 pounds, and he'd never had a client release a fish that big. I told my father in law that he should be proud to know that hen would get to spawn and make lots more steelhead with the genes to grow into giants.
We went on to catch 3 more fish that day, one around 5-6 pound, and two that were in the 13-15 pound range. We released them all, and the guide kept apologizing for the slow fishing. Heck, it was the best day of steelie fishing I'd ever enjoyed, but he said it was very poor fishing. I had some buddies fishing the south fork of the Umpqua that day, while we were on the north fork. They caught 23 or 24 fish between the two boats that day.